Electric fuse



C. ROSSO June 13, 1961 ELECTRIC FUSE Filed June 29, 1959 INVENTOR. Char/es R0550 A T TORNEYS United "States Patent I) 2,988,619 ELECTRIC FUSE Charles Rosso, Cimarron, N. Mex. Filed June 29, 1959, Ser. No. 823,550 6 Claims. (Cl. 200-130) suited to such use. For some fuse installations, especially when the fuse is employed in a direct current circuit, it is necessary to prevent short-circuiting of the current path because of arcing on the occurrence of melting of the fuse and, accordingly, it is an object of the present invention to provide a plug type electric fuse of improved construction havinga readily visible fusible element and capable of withstanding heavy vibration and sudden periodic temperature changes and which minimizes the likelihood of continued passage ofcurrent because of arcing after melting of the fusible element.

' Briefly, in carrying out the objects of this invention in one embodiment thereof a plug type fuse is provided which includes a base having electrical contacts and an insulating support member extending from the base with a U-shaped fusible element extending around the outer side of the support. The support and fusible element are enclosed within a transparent envelope and are visible from all directions. The envelope is provided with a groove which accommodates the fuse element and the envelope is in engagement with the support along the sides of the element so that an elongated passage is formed and communication between opposite ends or sides of the fusible element is prevented except through the passage.

In another embodiment the transparent envelope has a cylindrical interior surface and the fusible element is accommodated in a groove in the insulating support which support fits tightly within the transparent envelope so that it engages the envelope on both sides of the groove to form a single elongated passage as in the first embodiment.

The features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this specification. The invention itself, however,'both as to its organization and method of operation, will be more readily understood from the following description taken in connection with the accompanying drawing, in which:

FIG. 1 is an elevation view of a plug type fuse embody- .ing the invention;

FIG. 2 is a longitudinal sectional view of the fuse of FIG. 1;

FIG. 3 is a sectional elevation view along the line 3-3 of FIG. 2;

FIG. 4 is a longitudinal sectional view similar to FIG. 2 illustrating another embodiment of the invention; and

FIG. 5 is a sectional view along the line 5-5 of FIG. 4.

Referring now to the drawings, the plug type fuse illus trated in FIGS. 1, 2 and 3 comprises a base having metal pins 11 mounted in an electrically conducting metal sleeve 12 forming the outer walls of the base. The pins 11 are provided to secure the base in a bayonet type socket in the usual manner. The base is provided with a center contact or pin 13 and the sleeve 12 provides the other contact. An elongated fusible element is supported within a transparent cylindrical envelope 14 secured at one end within the base 10 and the element is carried on an elongated cylindrical insulating support 15 which fits closely within the envelope 14 in engagement with the inner wall thereof. Both the envelope and the support have been shown as having spherical end portions thereby affording a maximum length of the fusible element.

The fusible element indicated at 16 in FIGS. 2 and 3 fits on the outer wall of the cylindrical center support 15 and the envelope 14 is provided with a recess or groove indicated at 17 which extends entirely about the support 15 and thus forms a continuous elongated passage about the fuse element 16. One end of the element 16 is connected to one of the pins 11 by a lead 18 and the other end is connected to the contact 13 by a lead 19.

The envelope 14 is made of glass or a suitable transparent plastic which may be molded to provide the groove 17 and the end of the envelope 14 is sealed within the base 10 by an end piece or closure 21 of the same material as the envelope and which is sealed to the envelope by fusing or cementing in a manner to completely close the space within the envelope and to hold the support 15 securely in position. The base 10 within the metal sleeve 12 is filled with a suitable cement or plastic 22 which forms a rigid body for the base and retains the contact 13 securely in position.

The sides of the support 15 adjacent the groove 17 are in substantially continuous engagement with the envelope 1 14 and prevent the passage of ionized gas around the support 15 except through the passage within the recess 17. Arcing across of the current upon rupture of the fuse is thus prevented and effective breaking of the circuit is assured since the only passage of current must be along the fuse length and arcing would result in further melting of the link and quick interruption of the current due to the increased length of the are.

In the second embodiment of the invention illustrated in FIGS. 4 and 5 the construction is essentially similar to that of the first embodiment and corresponding parts have been designated by the same numerals with the suffix letter a.

The transparent envelope 14a in this embodiment may be made of glass or a plastic material similar to that of the first embodiment. In this embodiment the insulated support indicated at 15a is formed integrally with the base 10a and is constructed to have cylindrical surfaces in engagement with the inner wall of the envelope 14a and is flat on two sides. The support 15a is provided with a longitudinal groove 25 which is formed in the cylindrical surfaces and extends completely about the support; the fusible element indicated at 1611 is carried on the support 15a within the groove 25. The sides of the support 15a adjacent the groove 25 are in substantially full engagement with the inner wall of the envelope 14a and thus form a closed passage throughout the length of the fusible element 16a corresponding to the passage formed by the groove 17 in the first embodiment.

It may be desirable to provide for the escape of gases under pressure upon melting of the fuse link and the passage 25 of this embodiment has been illustrated as provided with openings for communication with the exterior. These openings, indicated at 26 and 27, are formed as slots in the base 10a closed on their upper sides by the end of the envelope 14a and are in open communication with the outside through central openings provided in the pins 11a. The operation of the fuse of FIGS. 4 and 5 is essentially the same as that of the first embodiment and acts to prevent arcing across between the two legs of the passage and assures interruption of the current upon fusing of the element 16a in the same manner as the embodiment of FIG. 1.

While the invention has been described in connection with the details of construction of specific fuses, other applications and embodiments will occur to those skilled geese 1e 3 inthe art; therefore, it is not desired that, theinvention be limited to the details illustrated and described and it is intended by the appended claims to cover all modifications which fall within the spirit and scope of the invention.

I claim:

1. A plug type fuse comprising a base, anelongated support member of insulating material extending from said base, an elongated substantially U-shaped fusible element extending along both sides of said support and across the outer end thereof, external electric contacts 'on said base, conducting means connecting the ends of saidelement and respective ones of said contacts, and means including a transparent envelope secured in said base and having wall portions engaging said support continuously along both sides of said element to provide an elongated passage from one end of said element to the other to prevent cross-communication between zones adjacent said element on opposite sides of said support except through said passage extending substantially throughout the length of said support.

2. A plug type fuse as set forth in claim 1 wherein said support conforms to the inner walls of said envelope substantially throughout its length and said envelope is provided with a recess extending along said support for cooperation with said support to form said passage.

3. A plug type fuse as set forth in claim 1 wherein said support conforms to the inner wall of said envelope adjacent the fusible element and is recessed to accommodate said element and to cooperate with said envelope to form said passage.

4. A plug type fuse as set forth in claim 1 wherein said support conforms to and fits closely against the inner wall throughout the length of said fusible element and is provided with a groove accommodating said element and cooperating with said envelope to form said passage.

5. A plug type fuse comprising a base, an elongated support member of insulating material extending from said base, an elongated substantially U-shaped fusible element extending along both sides of said support and around the outer end thereof, external electric contacts on said base, conducting means connecting the ends of said element and respective ones of said contacts, and means including a transparent envelope secured in said base and having wall portions engaging said support continuously along both sides and across the bottom of said element to provide an uninterrupted elongated passage from one end of said element to the other to prevent cross-communication between zones adjacent said element on opposite sides of said support except through said passage extending substantially throughout the length of said support, and pressure relief means communicating with the atmosphere from said passage for relief of gas under pressure generated upon melting of the fuse link.

6. A plug type fuse as set forth in claim 5 in which the end portions of the envelope and the support are generally spherical end portions thereby affording amaximum length of fusible element.

References Cited in the fileof this patent UNITED STATES PATENTS 943,698 Murray Dec. 21, 1909 1,061,894 Baker May13, 1913 2,309,013 Rawlins et a1. Jan. 19, 1943 2,900,475 Rosso Aug. 18, 1959 

